# So where did the Orinoco River used to go?

**URL:** <https://boards.straightdope.com/t/so-where-did-the-orinoco-river-used-to-go/343016>\
**Category:** Factual Questions\
**Created:** [February 4, 2006, 8:01pm UTC](https://boards.straightdope.com/t/so-where-did-the-orinoco-river-used-to-go/343016 "2006-02-04T20:01:17Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\
**Post date:** [February 4, 2006, 8:01pm UTC](https://boards.straightdope.com/t/so-where-did-the-orinoco-river-used-to-go/343016/1 "2006-02-04T20:01:17Z")

</div>

OK, here’s the background: As I understand it, the Amazon River at one time in the geologic past used to flow East to West, emptying somewhere near modern Peru or Ecuador. Then, the formation of the Andes Mountains blocked off the oulet, causing it to form a giant inland sea, which ultimately found another outlet, which was to the East.

In addition, as I understand it, it’s thought that in the distant past, when Africa and South America were one continent, that what is the modern Congo would have flowed into the modern Amazon–which would have made one MF of a river!

Anyway, the Orinoco meets the ocean in Northern Venezuela. In the distant geologic past–when SA and Africa were one island–that would have been somewhere in the modern Guinea/Sierra Leone/Liberia area. Is there any geologic evidence to suggest that the modern day Orinoco existed at that time, and the it had a flow thru Western Africa?

(And feel free to correct any misconceptions I might be under. I come here to learn.)

---

<div class="post-metadata">

**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\
**Post date:** [February 4, 2006, 10:47pm UTC](https://boards.straightdope.com/t/so-where-did-the-orinoco-river-used-to-go/343016/2 "2006-02-04T22:47:40Z")

</div>

Well, I think that on these geologic scales, we would be more accurately discussing the _drainage basins_ in Gondwana that correspond to the modern Congo, Amazon, Orinoco, Gambia or Niger basins, as opposed to the specific river, which could get radically rerouted as a consequence of uplift and subduction.

As it is, the Orinoco and Amazon basins do connect south of Venezuela through the Casiquiare, river an Orinoco affluent that splits and then flows into the Rio Negro, an Amazon tributary. The Guyana and eastern Brazilian highlands are geologically much older than the Andes. It is theorized that at some point in the past, the Orinoco, Amazon, and Paraná/Plata basins _all_ together formed a shallow sea.